1. Field of the Invention
The present invention relates to fluid current conveyors and, more particularly, to a captive multilateral carrier for a pneumatic transport tube system.
2. Discussion of the Related Art
Pneumatic transport tube systems transfer materials between stations by moving a carrier inside a transport tube. The carrier is moved by creating a pneumatic pressure drop across the carrier which creates a force on one or the other end of the carrier thereby moving the carrier through the transport tube. More common transport tube systems are used in banks in which a cylindrical removable carrier is used to transfer materials between a teller terminal inside the bank and a customer terminal accessible by a customer in a vehicle. Captive carrier pneumatic transport systems are typically used for heavy payloads. Since the carrier and transport tube are a larger size for the heavy payload, the transport tube is run overhead instead of underground which is common with smaller systems.
A heavy payload may be up to 25 lbs. (11.5 Kg), and the carrier itself may weight 16 lbs (7.5 Kg). One example of a heavy payload captive carrier system is shown in U.S. Pat. No. 5,131,792, which discloses a cylindrical captive carrier. The top of the carrier is automatically removed and held within the terminal unit and the carrier is then pivoted for presentation to the user. That design requires a relatively complex mechanism to remove the end cover of the carrier, store it and reinstall the end cover after the carrier is pivoted back into the terminal unit.
Another example of a heavy payload captive carrier is disclosed in U.S. Pat. No. 4,792,263. Here, a rectangular captive carrier is disclosed comprising a hollow rectangular body, the ends of which are closed by sliding end plates. The carrier rotates 90.degree. as it moves between the two terminal units. That rotation results in the carrier being opened with two different mechanisms depending on which terminal unit is being used. For example, at the customer terminal unit, the carrier is pivoted outwardly toward the customer; and then, a sliding cover on the terminal unit slides an end plate parallel to the major axis of the end plate thereby opening the carrier for use by the customer. At the teller terminal, the carrier is received in a sliding drawer and slides outward toward the teller in a direction parallel to the major axis of the end plate. The end plate is locked in position, and therefore, the carrier is opened as it slides out toward the teller. The end plates are positively locked in a closed position when the carrier is traveling between the terminal units. A mechanism within the terminal unit releases the end plate locks as the carrier comes to rest in the terminal unit.
The above '263 design has the disadvantage of requiring a two-step opening procedure for the carrier at the customer terminal unit which is relatively slow and complicated. Further, the rectangular profile of the carrier results in a 90.degree. change of orientation as the carrier moves between the customer and teller terminal units. Finally, the locking mechanism for the carrier end plates is complicated with many moving parts and has a risk of interference from debris.